Cutter members for dry shavers



Aug. 3, 1965 N- T. SANDERS 3,197,864

CUTTER MEMBERS FOR DRY SHAVERS Filed July 16, 1963 ,NVENTDR.

United States Patent 3,197,864 CUTTER MEMBERS FOR DRY SHAVERS Norman Thomas Sanders, Studley, England, assignor to Needle industries Limited, Birmingham, England, a British company Filed July 16, 1963, Ser. No. 295,417 Claims priority, application Great Britain, July 18, 1962, 27,519/62 2 (llaims. (Cl. 30-416) This invention relates to cutters or shavers (hereinafter referred to for convenience as shavers) comprising an apertured guard member in the form of a foil plate or equivalent member having an outer face for placing an face-to-face relation with the surface to be shaved and a cutter member disposed at the inner face of the guard member and movable over the inner face thereof In my co-pending application 335,438, I have described such a shaver wherein the cutter member comprises one or more blade elements each in the form of a concave shell having an open mouth at its concave side and I have described and illustrated a shell of this kind which is of conical or frustoconical form.

The object of the present invent-ion is to provide an improvement in or modification in the means for mounting the blade elements of the shaver described in my above mention co-pending application.

I have found that where these are of frust-o-conical form as disclosed in my co-pending application and are mounted on a carrier member as therein disclosed by means of a fastening element in the form of a rivet extending through a hole at the narrower lower apex of the conical or frusto-conical blade element, two possible disadvantages are encountered neither of which prevents operation of the shaver but which it is preferable to avoid.

The first of these is that the positioning of the hole at the apex is critical in that any lateral displacement between this hole and the axis of the conical or frusto-conical blade element may limit or even eliminate the desired freedom of rocking movement and floating movement of the blade element relatively to a carrier on which it is mounted.

Secondly the existence of an annular space of wedge shape in cross-section between the face of the carrier member and the outer face of the blade element opposed thereto inherently provides the possibility of shaved material filling this space and obstructing free rocking .and floating movement of the blade element. Sue-h movement is necessary to ensure proper contact between the contact face of the blade element and the inner face of the guard member especially when the latter is subject to elastic deflection as previously mentioned.

The modification or improvement in accordance with the present invention therefore comprises the provision of a locally raised part or element on the carrier member immediately adj awn-t to a hole in the or each blade element through which extends a rivet or fastening element serving to connect the blade element to the carrier member whilst at least the marginal portion surrounding the hole of the or each blade element so mounted on the carrier is made of curved concave form so that such marginal port-ion is substantially parallel to the adjacent opposed face of the raised part or element of the carrier member.

The height of the raised portion or element thus provides a satisfactorily large clearance between the outer face of the blade element and the carrier member which avoids or materially reduces the risk of clogging and obstruction by shaved material.

Moreover, due to the parallel relation between the margin of the blade element around the hole therein and the opposed face of the raised part or element the posi- 3,197,864 Patented Aug. 3, 1965 tion of the hole in relation to the axis of the blade element is not critical and consequently facilitates protection of the blade element andreduces cos-t of manufacture.

The improvement will now be described by way of example with reference to a specific embodiment illustrated in the accompanying drawings wherein:

FIGURE 1 is a fragmentary view in cross-section of a shaver showing the assembly of guard member and cutter incorporating the improvement, and

FIGURE 2 is a fragmentary view on an enlarged scale showing a portion of one of the blade elements of the cutter member and the manner of mounting same on its associated carrier member.

The shaver may be of the general form and construction described and claimed in my co-pending application No. 335,438 except for the modifications or improvements now described. The shaver thus comprises a body 10 in the form of a hollow chamber in which is accommodated an electric motor and a battery therefor (not shown).

The motor has a spindle 12 on which is mounted a cutter member 13 cooperating with an apertured guard member 14 detachably mounted on the body of the shaver by means of a supporting structure comprising an inner component in the form of a ring 15 and an outer compo nent in the form of a clamping ring 16. The clamping ring 16 is slid able axially on the wall 17 of a cylindrical chamber at the end of the body, the fit being such that the clamping ring 16 and hence the guard member is normally retained frictionally in assembled relation with the body.

The blade elements 18, as best seen in FIGURE 2, are made from a plain carbon steel capable of being hardened and tempered. Typically steel strip having a carbon content of 1.3% may be employed. Before hardening and tempering, the blades are shaped by pressing into cupshaped forms of curved concave shape as viewed from the upper side. The inner and outer surfaces 20 and 21 may be portions of spheres, but spherical configuration is not critical and any suitable curved surface concave at its upper side and hence convex at its underside may be adopted.

The upper edge of each blade element forms a contact face 22 which is pressed against the inner face of the guard member 14 by means of a spring 23 acting on the underside of the carrier member 19 and retained at its lower end by a bushing 24 on the spindle 12. The upper end portion of the spindle is formed, as described and claimed in said co-pending application 335,438 with a head 25 of larger cross-sectional dimensions than an aperture of square shape in the carrier member 9 which is slidably mounted on a corresponding square end 26 of the spindle, there being a clearance between the underside of the head 25 and the upper side of the carrier member 19 so that the pressure of the spring acts to produce pressure contact between the contact faces 22 of the blade elements and the inner face of the guard member 14.

In the course of heat treatment, namely heating of the blade elements preparatory to quenching for the purpose of hardening the blade elements, and then further heating the blade elements to a lower temperature to produce tempering of the blade elements all in accordance with known practice, there is an inevitable tendency for some degree of de-carburisation to take place. This occurs over the surface layers of the blade element including the surface layer adjacent to the inner face 20, the outer face 21, and to the contact face 22.

Such de-carburisation is not of critical importance so far as the surface layer adjacent to the inner face 20 is concerned, but the shaving performance of the shaver is dependent upon the maintenance of a sharp edge at the intersection of the contact face 22 and the outer face 21 and de-carburisation in this region reduces the hardness f the blade element so that the edge will become blunt more rapidly than would otherwise be the case.

Accordingly I remove part of the material at the outer face 21 in the locality of the contact face 22. The material removed is that which lies between the continued or extrapolated surface 27 as shown in broken lines and the newly formed frusto-conical surface 30.

The included angle made between the axis 23 of the blade element and the generatrix 29 which forms the frusto-conical surface 30" now present at the outer surface of the blade element adjacent to its contact face 22 may be in the range 35 to 45 degrees, a preferred value being about 4-0 degrees.

The blade element may be made of material having a thickness of 0.005 inch and the width of the contact face 22, if no material were removed Within the surface 27, would then be of the order of 0.0075 inch.

The amount of material removed between the surfaces 27 and 3t? is preferably such as to reduce the radial width of the contact face 22 to a value of 0.002 inch or rather less than one-third of What it would otherwise be.

It will of course be understood that the contact face 22 itself is formed by grinding against a frat plane abrasive surface, or possibly a convex spherical abrasive surface having a radius of curvature which is large compared with that of the inner and outer faces '20 and 21 of the blade element itself, so that in this way material is in any 7 case removed from the blade element adjacent to the contact face over at least a layer having a thickness equal to the impoverished or de-carburised layer at the contact face 22.

The amount of material removed between the surfaces 27 and 30 is more than adequate to remove de-carburised or impoverished material from the region of the cutting edge 30a so that the latter is enabled to remain sharp for an extended period of service.

Reduction in the width of the contact face 22 has also important advantages .when applied to a shaver of which the electric motor is driven from batteries accommodated in the body of the shaver and when used in conjunction with a guard member as hereinafter referred to.

The guard member 14 is maintained in fiat, plane form by radial tension set up by gripping a skirt portion 31 of the guard member between the inner ring 15 and the outer clamping ring 16 as described in my application Serial No. 199,865 (now abandoned). This enable thin material to be employed for the guard member which typically may be made of alloy steel or plain carbon steel in the form of a hard rolled sheet having a thickness not less than 0.001 inch, a preferred value being about 0.002 inch.

The employment of this form of guard member necessarily entails acceptance of the fact that when in use inward pressure against the outer surface of the guard member when the shaver is held against the users face will produce some inward elastic deflection of the guard member so that theinner face thereof is no longer of strictly flat plane form.

It is found that reduction in the radial width of the contact face 22 as described andillustrated produces a surprising degree of improvement in shaving performance. This may be due to reduction, or nearlycomplete elimination, of any tendency for the contact face of the blade element to part or move out of contact with the inner surface of the guard member, even when the guard member is pressed firmly against the face and is subjected to elastic deflection.

Moreover, this reduction in radial width is extremely beneficial in maintaining low frictional resistance to rotation of the cutter member under varying conditions of use.

It will be understood that some degree of lubrication usually exists between the contact face 22 and the inner face of the guard member by virtue of greasy or oily substances derived from the skin of the user and which find their way onto the inner face of the contact member. If, however, the contact face 22 is'of undue radial width this can create a suction effect when a given blade element has been in use for an extended period of time and has become very accurately lapped to the inner face of the guard member. Such suction effect will very greatly increase the resistance to rotation and hence the current drawn from the battery by the motor.

Additionally, conditions arise especially after replacement of a blade element in which the rapid attainment of efiicient shaving performance is materially assisted by the reduction in radial width of the contact face 22.

With a relatively wide face such as would be present were no material removed between the surfaces 27 and 30, lapping of the contact face 22 to the inner face of a guard member which had already undergone an extended period of service would take an appreciable time whereas with a narrower face such lapping is more rapidly performed.

Finally under all conditions of use the reduction in radial width of the contact face 22 increases the specific contact pressure between this face and the inner face of the guard member and improves the shaving performance.

According to the invention there is provided an improvement in the manner of mounting the blade elements 13 on the carrier member 1%.

For this purpose the carrier member 19 is formed with raised portions 31. These may be produced by a pressing operation which causes the metal to be displaced in the manner of a shearing operation without, however, completing such shearing so that there is formed on the underside of the carrier member a cavity 32. the depth of which is approximately equal to the height of the raised portion 31.

The carrier member 19 may be made of high carbon steel which is capable of being hardened and tempered so that it can slide easily on the square end 26 and is resistant to any Wear at the edges of the aperture through which the square end 26 passes. The latter is also made of steel which is hardened to resist wear.

Displacement of metal to produce the raised portions 3 is carried out before hardening and tempering. it may, and often does, result in the physical rupture of the raised metal from the surrounding part, the raised portion however remaining in situ by virtue of'the mechanical interference between the claims of metal at the shearing plane. fter hardening and tempering the mechanically intervening grains become locked with each other so that the raised portion is then irremovably held in position.

The blade element has a hole 33 formed coaxially with its own axis and through this hole extends the upper portion 34 of the shank 134 of a rivet 234. This shank is of tapering form and its lower portion 35 is thus positively located in a tapering hole 135 formed in the raised portion 31 of the carrier member 19. The blade element is held on the rivet 234 by the head 37 thereof which comprises abutment means and is spaced above the raised portion 31 by a distance greater than the thickness of the blade element around the hole 33.

The rivet 234 comprises a fastening element and is formed of case hardened steel but the lower end of the rivet which protrudes into the cavity 32 can be deformed by endwise pressure to form a laterally spread portion or an elementary head 38, by virtue of the fact that the case hardened layer thereof, sufficiently resistant to withstand bearing wear at the locality at which it is subject to this, that is where it passes throughthe hole 33, is capable of disruption or bursting under mechanical stress to form the head 33. This head in combination with the tapering form of the shank 134 thus holds the rivet positively against movement relatively to the carrier member, whilst there is freedom for the blade element to have limited floating movement and limited rocking movement relatively to the rivet and carrier member. By floating movement is meant vertical displacement of the blade element, and by rocking movement is meant that the blade element can tilt about any axis at right angles to the axis 23 and passing therethrough. For this purpose it will be understood that the diameter of the hole 33 is greater than the diameter of the upper portion 34 of the rivet shank so as to provide the necessary radial clearance between these two parts.

Two main advantages are achieved by this construction.

Firstly the adoption of a cup-shaped concave shell of curved form in cross-section results in the marginal portions 40 which border the hole 33 being horizontal, that is to say parallel or nearly parallel to the upwardly presented face of the raised part 31 so that there is only a slight, if any, gap between the under face of the marginal portions 40 and the upper face of the raised part 31. Consequently the possibility that material shaved from the users face, that is hairs and skin particles, may so clog the joint between the carrier member 19 and the blade element that the latter can no longer rock or flow, is materially reduced.

Such rocking or floating movement is important to allow the contact face 22 to conform accurately with and hence maintain contact with the inner face of the guard member 14 notwithstanding inward elastic deflection thereof when the shaver is in use.

Moreover, the fact that the marginal portions 40 as defined by the inner and outer fiaces of the concave shell are at right angles or substantially so to the axis 28 avoids the necessity for maintaining a critically coincident relation between the axis 28 (which is the axis of the cutting edge 30a) and the axis of the hole 33. Small lateral displacements between these two axes do not produce a member include-s any number of arms although for convenience it has been illustrated in relation to a two arm cutter member carrying two blade elements 18.'

What I claim then is:

1. In a shaver comprising a body, a thin-walled apertured guard member thereon, and a cutter member movable in contact with said guard member over its inner 'said guard member and in combination with said outer face defining a cutting edge, said blade element having a hole therein at a position centrally of said blade element at its end remote from said mouth, a fastening element extending from said raised portion and through said hole with later-a1 clearance, and abutment means on said fastening element at a distance above said raised element greater than the wall thickness of said blade element adjacent to skewed or oblique hole 33 as would be the case were the for practical purposes, the risk of any clogging and ob- V struction to floating or rocking movement of the blade element from the causes previously mentioned. The height of the raised part 31 may typically be ofthe order of 0.01 inch but this may be increased if desired according to the thickness of the material employed for the construction of the carrier member 19.

It will be understood that the modifications or improvements above described may be applied where the cutter said hole whereby said blade element can both rock and float-relatively to said carrier member.

2. In a shaver comprising a body, a thin-walled apertured guard member thereon, and a cutter member movable in contact with said guard member over its inner face; the structure claimed in claim 1 wherein said locally raised portion has a hole formed therethro'ugh to receive said fastening element, and wherein both said fastening element and said hole in said raised element tapercon vergently in a direction away from said blade element, said fastening element being case-hardened and incorporating a laterally spread portion at that side of said carrier member remote from said blade element to hold said fastening element fixedly against both axial and lateral displacement relatively to said carrier member.

References Cited by the Examiner UNITED STATES PATENTS 2,213,291 9/40 Testi 30-432 2,283,038 5/42 Breitenstein 30-43 .9 2,566,214 -8/5=1 Knowles 3043.7 2,690,008 9/54 Bobkowicz 30-436 2,900,719 '8/59 Kohner et a1.

FOREIGN PATENTS 978,929 11/50 France.

WILLIAM FELDMAN, Primary Examiner.

MYRON C. KRUSE, Examiner. 

1. IN A SHAVER COMPRISING A BODY, A THIN-WALLED APERTURED GUARD MEMBER THEREON, AND A CUTTER MEMBER MOVABLE IN CONTACT WITH SAID GUARD MEMBER OVER ITS INNER FACE; THE IMPROVEMENT COMPRISING THE PROVISION IN SAID CUTTER MEMBER OF A CARRIER MEMBER HAVING AT LEAST ONE LOCALLY RAISED PORTION FOR THE MOUNTING OF A BLADE ELEMENT, A BLADE ELEMENT IN THE FORM OF A CURVED CUP-SHAPED SHELL HAVING INNER AND OUTER FACES AND HAVING AN OPEN MOUTH AT ITS CONCAVE SIDE BOUNDED BY A CONTACT FACE CONTACTING SAID GUARD MEMBER AND IN COMBINATION WITH SAID OUTER FACE DEFINING A CUTTING EDGE, SAID BLADE ELEMENT HAVING A HOLD THEREIN AT A POSITION CENTRALLY OF SAID BLADE ELEMENT AT ITS END REMOTE FROM SAID MOUTH, A FASTENING ELEMENT EXTENDING FROM SAID RAISED PORTION AND THROUGH SAID HOLE WITH LATERAL CLEARANCE, AND ABUTMENT MEANS ON SAID FASTENING ELEMENT AT A DISTANCE ABOVE SAID RAISED ELEMENT GREATER THAN THE WALL THICKNESS OF SAID BLADE ELEMENT ADJACENT TO SAID HOLE WHEREBY SAID BLADE ELEMENT CAN BOTH ROCK AND FLOAT RELATIVELY TO SAID CARRIER MEMBER. 